1//===--- ExprClassification.cpp - Expression AST Node Implementation ------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements Expr::classify. 11// 12//===----------------------------------------------------------------------===// 13 14#include "clang/AST/Expr.h" 15#include "clang/AST/ASTContext.h" 16#include "clang/AST/DeclCXX.h" 17#include "clang/AST/DeclObjC.h" 18#include "clang/AST/DeclTemplate.h" 19#include "clang/AST/ExprCXX.h" 20#include "clang/AST/ExprObjC.h" 21#include "llvm/Support/ErrorHandling.h" 22using namespace clang; 23 24typedef Expr::Classification Cl; 25 26static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 27static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 28static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 29static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 30static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 31static Cl::Kinds ClassifyConditional(ASTContext &Ctx, 32 const Expr *trueExpr, 33 const Expr *falseExpr); 34static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 35 Cl::Kinds Kind, SourceLocation &Loc); 36 37Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 38 assert(!TR->isReferenceType() && "Expressions can't have reference type."); 39 40 Cl::Kinds kind = ClassifyInternal(Ctx, this); 41 // C99 6.3.2.1: An lvalue is an expression with an object type or an 42 // incomplete type other than void. 43 if (!Ctx.getLangOpts().CPlusPlus) { 44 // Thus, no functions. 45 if (TR->isFunctionType() || TR == Ctx.OverloadTy) 46 kind = Cl::CL_Function; 47 // No void either, but qualified void is OK because it is "other than void". 48 // Void "lvalues" are classified as addressable void values, which are void 49 // expressions whose address can be taken. 50 else if (TR->isVoidType() && !TR.hasQualifiers()) 51 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); 52 } 53 54 // Enable this assertion for testing. 55 switch (kind) { 56 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 57 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 58 case Cl::CL_Function: 59 case Cl::CL_Void: 60 case Cl::CL_AddressableVoid: 61 case Cl::CL_DuplicateVectorComponents: 62 case Cl::CL_MemberFunction: 63 case Cl::CL_SubObjCPropertySetting: 64 case Cl::CL_ClassTemporary: 65 case Cl::CL_ArrayTemporary: 66 case Cl::CL_ObjCMessageRValue: 67 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 68 } 69 70 Cl::ModifiableType modifiable = Cl::CM_Untested; 71 if (Loc) 72 modifiable = IsModifiable(Ctx, this, kind, *Loc); 73 return Classification(kind, modifiable); 74} 75 76/// Classify an expression which creates a temporary, based on its type. 77static Cl::Kinds ClassifyTemporary(QualType T) { 78 if (T->isRecordType()) 79 return Cl::CL_ClassTemporary; 80 if (T->isArrayType()) 81 return Cl::CL_ArrayTemporary; 82 83 // No special classification: these don't behave differently from normal 84 // prvalues. 85 return Cl::CL_PRValue; 86} 87 88static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, 89 const Expr *E, 90 ExprValueKind Kind) { 91 switch (Kind) { 92 case VK_RValue: 93 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue; 94 case VK_LValue: 95 return Cl::CL_LValue; 96 case VK_XValue: 97 return Cl::CL_XValue; 98 } 99 llvm_unreachable("Invalid value category of implicit cast."); 100} 101 102static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 103 // This function takes the first stab at classifying expressions. 104 const LangOptions &Lang = Ctx.getLangOpts(); 105 106 switch (E->getStmtClass()) { 107 case Stmt::NoStmtClass: 108#define ABSTRACT_STMT(Kind) 109#define STMT(Kind, Base) case Expr::Kind##Class: 110#define EXPR(Kind, Base) 111#include "clang/AST/StmtNodes.inc" 112 llvm_unreachable("cannot classify a statement"); 113 114 // First come the expressions that are always lvalues, unconditionally. 115 case Expr::ObjCIsaExprClass: 116 // C++ [expr.prim.general]p1: A string literal is an lvalue. 117 case Expr::StringLiteralClass: 118 // @encode is equivalent to its string 119 case Expr::ObjCEncodeExprClass: 120 // __func__ and friends are too. 121 case Expr::PredefinedExprClass: 122 // Property references are lvalues 123 case Expr::ObjCSubscriptRefExprClass: 124 case Expr::ObjCPropertyRefExprClass: 125 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 126 case Expr::CXXTypeidExprClass: 127 // Unresolved lookups get classified as lvalues. 128 // FIXME: Is this wise? Should they get their own kind? 129 case Expr::UnresolvedLookupExprClass: 130 case Expr::UnresolvedMemberExprClass: 131 case Expr::CXXDependentScopeMemberExprClass: 132 case Expr::DependentScopeDeclRefExprClass: 133 // ObjC instance variables are lvalues 134 // FIXME: ObjC++0x might have different rules 135 case Expr::ObjCIvarRefExprClass: 136 case Expr::FunctionParmPackExprClass: 137 case Expr::MSPropertyRefExprClass: 138 return Cl::CL_LValue; 139 140 // C99 6.5.2.5p5 says that compound literals are lvalues. 141 // In C++, they're prvalue temporaries. 142 case Expr::CompoundLiteralExprClass: 143 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType()) 144 : Cl::CL_LValue; 145 146 // Expressions that are prvalues. 147 case Expr::CXXBoolLiteralExprClass: 148 case Expr::CXXPseudoDestructorExprClass: 149 case Expr::UnaryExprOrTypeTraitExprClass: 150 case Expr::CXXNewExprClass: 151 case Expr::CXXThisExprClass: 152 case Expr::CXXNullPtrLiteralExprClass: 153 case Expr::ImaginaryLiteralClass: 154 case Expr::GNUNullExprClass: 155 case Expr::OffsetOfExprClass: 156 case Expr::CXXThrowExprClass: 157 case Expr::ShuffleVectorExprClass: 158 case Expr::IntegerLiteralClass: 159 case Expr::CharacterLiteralClass: 160 case Expr::AddrLabelExprClass: 161 case Expr::CXXDeleteExprClass: 162 case Expr::ImplicitValueInitExprClass: 163 case Expr::BlockExprClass: 164 case Expr::FloatingLiteralClass: 165 case Expr::CXXNoexceptExprClass: 166 case Expr::CXXScalarValueInitExprClass: 167 case Expr::UnaryTypeTraitExprClass: 168 case Expr::BinaryTypeTraitExprClass: 169 case Expr::TypeTraitExprClass: 170 case Expr::ArrayTypeTraitExprClass: 171 case Expr::ExpressionTraitExprClass: 172 case Expr::ObjCSelectorExprClass: 173 case Expr::ObjCProtocolExprClass: 174 case Expr::ObjCStringLiteralClass: 175 case Expr::ObjCBoxedExprClass: 176 case Expr::ObjCArrayLiteralClass: 177 case Expr::ObjCDictionaryLiteralClass: 178 case Expr::ObjCBoolLiteralExprClass: 179 case Expr::ParenListExprClass: 180 case Expr::SizeOfPackExprClass: 181 case Expr::SubstNonTypeTemplateParmPackExprClass: 182 case Expr::AsTypeExprClass: 183 case Expr::ObjCIndirectCopyRestoreExprClass: 184 case Expr::AtomicExprClass: 185 return Cl::CL_PRValue; 186 187 // Next come the complicated cases. 188 case Expr::SubstNonTypeTemplateParmExprClass: 189 return ClassifyInternal(Ctx, 190 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 191 192 // C++ [expr.sub]p1: The result is an lvalue of type "T". 193 // However, subscripting vector types is more like member access. 194 case Expr::ArraySubscriptExprClass: 195 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 196 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 197 return Cl::CL_LValue; 198 199 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 200 // function or variable and a prvalue otherwise. 201 case Expr::DeclRefExprClass: 202 if (E->getType() == Ctx.UnknownAnyTy) 203 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 204 ? Cl::CL_PRValue : Cl::CL_LValue; 205 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 206 207 // Member access is complex. 208 case Expr::MemberExprClass: 209 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 210 211 case Expr::UnaryOperatorClass: 212 switch (cast<UnaryOperator>(E)->getOpcode()) { 213 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 214 // [...] the result is an lvalue referring to the object or function 215 // to which the expression points. 216 case UO_Deref: 217 return Cl::CL_LValue; 218 219 // GNU extensions, simply look through them. 220 case UO_Extension: 221 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 222 223 // Treat _Real and _Imag basically as if they were member 224 // expressions: l-value only if the operand is a true l-value. 225 case UO_Real: 226 case UO_Imag: { 227 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 228 Cl::Kinds K = ClassifyInternal(Ctx, Op); 229 if (K != Cl::CL_LValue) return K; 230 231 if (isa<ObjCPropertyRefExpr>(Op)) 232 return Cl::CL_SubObjCPropertySetting; 233 return Cl::CL_LValue; 234 } 235 236 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 237 // lvalue, [...] 238 // Not so in C. 239 case UO_PreInc: 240 case UO_PreDec: 241 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 242 243 default: 244 return Cl::CL_PRValue; 245 } 246 247 case Expr::OpaqueValueExprClass: 248 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 249 250 // Pseudo-object expressions can produce l-values with reference magic. 251 case Expr::PseudoObjectExprClass: 252 return ClassifyExprValueKind(Lang, E, 253 cast<PseudoObjectExpr>(E)->getValueKind()); 254 255 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 256 // only specifically record class temporaries. 257 case Expr::ImplicitCastExprClass: 258 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 259 260 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 261 // whether the expression is an lvalue. 262 case Expr::ParenExprClass: 263 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 264 265 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 266 // or a void expression if its result expression is, respectively, an 267 // lvalue, a function designator, or a void expression. 268 case Expr::GenericSelectionExprClass: 269 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 270 return Cl::CL_PRValue; 271 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 272 273 case Expr::BinaryOperatorClass: 274 case Expr::CompoundAssignOperatorClass: 275 // C doesn't have any binary expressions that are lvalues. 276 if (Lang.CPlusPlus) 277 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 278 return Cl::CL_PRValue; 279 280 case Expr::CallExprClass: 281 case Expr::CXXOperatorCallExprClass: 282 case Expr::CXXMemberCallExprClass: 283 case Expr::UserDefinedLiteralClass: 284 case Expr::CUDAKernelCallExprClass: 285 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 286 287 // __builtin_choose_expr is equivalent to the chosen expression. 288 case Expr::ChooseExprClass: 289 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr()); 290 291 // Extended vector element access is an lvalue unless there are duplicates 292 // in the shuffle expression. 293 case Expr::ExtVectorElementExprClass: 294 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements()) 295 return Cl::CL_DuplicateVectorComponents; 296 if (cast<ExtVectorElementExpr>(E)->isArrow()) 297 return Cl::CL_LValue; 298 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase()); 299 300 // Simply look at the actual default argument. 301 case Expr::CXXDefaultArgExprClass: 302 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 303 304 // Same idea for default initializers. 305 case Expr::CXXDefaultInitExprClass: 306 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr()); 307 308 // Same idea for temporary binding. 309 case Expr::CXXBindTemporaryExprClass: 310 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 311 312 // And the cleanups guard. 313 case Expr::ExprWithCleanupsClass: 314 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 315 316 // Casts depend completely on the target type. All casts work the same. 317 case Expr::CStyleCastExprClass: 318 case Expr::CXXFunctionalCastExprClass: 319 case Expr::CXXStaticCastExprClass: 320 case Expr::CXXDynamicCastExprClass: 321 case Expr::CXXReinterpretCastExprClass: 322 case Expr::CXXConstCastExprClass: 323 case Expr::ObjCBridgedCastExprClass: 324 // Only in C++ can casts be interesting at all. 325 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 326 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 327 328 case Expr::CXXUnresolvedConstructExprClass: 329 return ClassifyUnnamed(Ctx, 330 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 331 332 case Expr::BinaryConditionalOperatorClass: { 333 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 334 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 335 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 336 } 337 338 case Expr::ConditionalOperatorClass: { 339 // Once again, only C++ is interesting. 340 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 341 const ConditionalOperator *co = cast<ConditionalOperator>(E); 342 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 343 } 344 345 // ObjC message sends are effectively function calls, if the target function 346 // is known. 347 case Expr::ObjCMessageExprClass: 348 if (const ObjCMethodDecl *Method = 349 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 350 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 351 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 352 } 353 return Cl::CL_PRValue; 354 355 // Some C++ expressions are always class temporaries. 356 case Expr::CXXConstructExprClass: 357 case Expr::CXXTemporaryObjectExprClass: 358 case Expr::LambdaExprClass: 359 case Expr::CXXStdInitializerListExprClass: 360 return Cl::CL_ClassTemporary; 361 362 case Expr::VAArgExprClass: 363 return ClassifyUnnamed(Ctx, E->getType()); 364 365 case Expr::DesignatedInitExprClass: 366 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 367 368 case Expr::StmtExprClass: { 369 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 370 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 371 return ClassifyUnnamed(Ctx, LastExpr->getType()); 372 return Cl::CL_PRValue; 373 } 374 375 case Expr::CXXUuidofExprClass: 376 return Cl::CL_LValue; 377 378 case Expr::PackExpansionExprClass: 379 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 380 381 case Expr::MaterializeTemporaryExprClass: 382 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 383 ? Cl::CL_LValue 384 : Cl::CL_XValue; 385 386 case Expr::InitListExprClass: 387 // An init list can be an lvalue if it is bound to a reference and 388 // contains only one element. In that case, we look at that element 389 // for an exact classification. Init list creation takes care of the 390 // value kind for us, so we only need to fine-tune. 391 if (E->isRValue()) 392 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 393 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 394 "Only 1-element init lists can be glvalues."); 395 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 396 } 397 398 llvm_unreachable("unhandled expression kind in classification"); 399} 400 401/// ClassifyDecl - Return the classification of an expression referencing the 402/// given declaration. 403static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 404 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 405 // function, variable, or data member and a prvalue otherwise. 406 // In C, functions are not lvalues. 407 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 408 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 409 // special-case this. 410 411 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 412 return Cl::CL_MemberFunction; 413 414 bool islvalue; 415 if (const NonTypeTemplateParmDecl *NTTParm = 416 dyn_cast<NonTypeTemplateParmDecl>(D)) 417 islvalue = NTTParm->getType()->isReferenceType(); 418 else 419 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 420 isa<IndirectFieldDecl>(D) || 421 (Ctx.getLangOpts().CPlusPlus && 422 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 423 424 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 425} 426 427/// ClassifyUnnamed - Return the classification of an expression yielding an 428/// unnamed value of the given type. This applies in particular to function 429/// calls and casts. 430static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 431 // In C, function calls are always rvalues. 432 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 433 434 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 435 // lvalue reference type or an rvalue reference to function type, an xvalue 436 // if the result type is an rvalue reference to object type, and a prvalue 437 // otherwise. 438 if (T->isLValueReferenceType()) 439 return Cl::CL_LValue; 440 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 441 if (!RV) // Could still be a class temporary, though. 442 return ClassifyTemporary(T); 443 444 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 445} 446 447static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 448 if (E->getType() == Ctx.UnknownAnyTy) 449 return (isa<FunctionDecl>(E->getMemberDecl()) 450 ? Cl::CL_PRValue : Cl::CL_LValue); 451 452 // Handle C first, it's easier. 453 if (!Ctx.getLangOpts().CPlusPlus) { 454 // C99 6.5.2.3p3 455 // For dot access, the expression is an lvalue if the first part is. For 456 // arrow access, it always is an lvalue. 457 if (E->isArrow()) 458 return Cl::CL_LValue; 459 // ObjC property accesses are not lvalues, but get special treatment. 460 Expr *Base = E->getBase()->IgnoreParens(); 461 if (isa<ObjCPropertyRefExpr>(Base)) 462 return Cl::CL_SubObjCPropertySetting; 463 return ClassifyInternal(Ctx, Base); 464 } 465 466 NamedDecl *Member = E->getMemberDecl(); 467 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 468 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 469 // E1.E2 is an lvalue. 470 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 471 if (Value->getType()->isReferenceType()) 472 return Cl::CL_LValue; 473 474 // Otherwise, one of the following rules applies. 475 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 476 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 477 return Cl::CL_LValue; 478 479 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 480 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 481 // otherwise, it is a prvalue. 482 if (isa<FieldDecl>(Member)) { 483 // *E1 is an lvalue 484 if (E->isArrow()) 485 return Cl::CL_LValue; 486 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 487 if (isa<ObjCPropertyRefExpr>(Base)) 488 return Cl::CL_SubObjCPropertySetting; 489 return ClassifyInternal(Ctx, E->getBase()); 490 } 491 492 // -- If E2 is a [...] member function, [...] 493 // -- If it refers to a static member function [...], then E1.E2 is an 494 // lvalue; [...] 495 // -- Otherwise [...] E1.E2 is a prvalue. 496 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 497 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 498 499 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 500 // So is everything else we haven't handled yet. 501 return Cl::CL_PRValue; 502} 503 504static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 505 assert(Ctx.getLangOpts().CPlusPlus && 506 "This is only relevant for C++."); 507 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 508 // Except we override this for writes to ObjC properties. 509 if (E->isAssignmentOp()) 510 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 511 ? Cl::CL_PRValue : Cl::CL_LValue); 512 513 // C++ [expr.comma]p1: the result is of the same value category as its right 514 // operand, [...]. 515 if (E->getOpcode() == BO_Comma) 516 return ClassifyInternal(Ctx, E->getRHS()); 517 518 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 519 // is a pointer to a data member is of the same value category as its first 520 // operand. 521 if (E->getOpcode() == BO_PtrMemD) 522 return (E->getType()->isFunctionType() || 523 E->hasPlaceholderType(BuiltinType::BoundMember)) 524 ? Cl::CL_MemberFunction 525 : ClassifyInternal(Ctx, E->getLHS()); 526 527 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 528 // second operand is a pointer to data member and a prvalue otherwise. 529 if (E->getOpcode() == BO_PtrMemI) 530 return (E->getType()->isFunctionType() || 531 E->hasPlaceholderType(BuiltinType::BoundMember)) 532 ? Cl::CL_MemberFunction 533 : Cl::CL_LValue; 534 535 // All other binary operations are prvalues. 536 return Cl::CL_PRValue; 537} 538 539static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 540 const Expr *False) { 541 assert(Ctx.getLangOpts().CPlusPlus && 542 "This is only relevant for C++."); 543 544 // C++ [expr.cond]p2 545 // If either the second or the third operand has type (cv) void, [...] 546 // the result [...] is a prvalue. 547 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 548 return Cl::CL_PRValue; 549 550 // Note that at this point, we have already performed all conversions 551 // according to [expr.cond]p3. 552 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 553 // same value category [...], the result is of that [...] value category. 554 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 555 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 556 RCl = ClassifyInternal(Ctx, False); 557 return LCl == RCl ? LCl : Cl::CL_PRValue; 558} 559 560static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 561 Cl::Kinds Kind, SourceLocation &Loc) { 562 // As a general rule, we only care about lvalues. But there are some rvalues 563 // for which we want to generate special results. 564 if (Kind == Cl::CL_PRValue) { 565 // For the sake of better diagnostics, we want to specifically recognize 566 // use of the GCC cast-as-lvalue extension. 567 if (const ExplicitCastExpr *CE = 568 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 569 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 570 Loc = CE->getExprLoc(); 571 return Cl::CM_LValueCast; 572 } 573 } 574 } 575 if (Kind != Cl::CL_LValue) 576 return Cl::CM_RValue; 577 578 // This is the lvalue case. 579 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 580 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 581 return Cl::CM_Function; 582 583 // Assignment to a property in ObjC is an implicit setter access. But a 584 // setter might not exist. 585 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 586 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 587 return Cl::CM_NoSetterProperty; 588 } 589 590 CanQualType CT = Ctx.getCanonicalType(E->getType()); 591 // Const stuff is obviously not modifiable. 592 if (CT.isConstQualified()) 593 return Cl::CM_ConstQualified; 594 595 // Arrays are not modifiable, only their elements are. 596 if (CT->isArrayType()) 597 return Cl::CM_ArrayType; 598 // Incomplete types are not modifiable. 599 if (CT->isIncompleteType()) 600 return Cl::CM_IncompleteType; 601 602 // Records with any const fields (recursively) are not modifiable. 603 if (const RecordType *R = CT->getAs<RecordType>()) { 604 assert((E->getObjectKind() == OK_ObjCProperty || 605 !Ctx.getLangOpts().CPlusPlus) && 606 "C++ struct assignment should be resolved by the " 607 "copy assignment operator."); 608 if (R->hasConstFields()) 609 return Cl::CM_ConstQualified; 610 } 611 612 return Cl::CM_Modifiable; 613} 614 615Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 616 Classification VC = Classify(Ctx); 617 switch (VC.getKind()) { 618 case Cl::CL_LValue: return LV_Valid; 619 case Cl::CL_XValue: return LV_InvalidExpression; 620 case Cl::CL_Function: return LV_NotObjectType; 621 case Cl::CL_Void: return LV_InvalidExpression; 622 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 623 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 624 case Cl::CL_MemberFunction: return LV_MemberFunction; 625 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 626 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 627 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; 628 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 629 case Cl::CL_PRValue: return LV_InvalidExpression; 630 } 631 llvm_unreachable("Unhandled kind"); 632} 633 634Expr::isModifiableLvalueResult 635Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 636 SourceLocation dummy; 637 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 638 switch (VC.getKind()) { 639 case Cl::CL_LValue: break; 640 case Cl::CL_XValue: return MLV_InvalidExpression; 641 case Cl::CL_Function: return MLV_NotObjectType; 642 case Cl::CL_Void: return MLV_InvalidExpression; 643 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 644 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 645 case Cl::CL_MemberFunction: return MLV_MemberFunction; 646 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 647 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 648 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; 649 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 650 case Cl::CL_PRValue: 651 return VC.getModifiable() == Cl::CM_LValueCast ? 652 MLV_LValueCast : MLV_InvalidExpression; 653 } 654 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 655 switch (VC.getModifiable()) { 656 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 657 case Cl::CM_Modifiable: return MLV_Valid; 658 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 659 case Cl::CM_Function: return MLV_NotObjectType; 660 case Cl::CM_LValueCast: 661 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 662 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 663 case Cl::CM_ConstQualified: return MLV_ConstQualified; 664 case Cl::CM_ArrayType: return MLV_ArrayType; 665 case Cl::CM_IncompleteType: return MLV_IncompleteType; 666 } 667 llvm_unreachable("Unhandled modifiable type"); 668} 669